The game DOES USE/APPLY Switch 2 HDR Calibration app settings.
Even if the game supports and reads system level HDR calibration, the Peak HDR Luminance is always a lot lower than what we've setup so the overall contrast of the image is flatter than it should be.
The game seems in fact to totally ignore the first Luminance slider/section of the system HDR Calibration app, but changes dynamically only when changing the second Paper White slider/section (giving the impression that also this Nintendo first party title has "fake HDR" or it wasn't graded with HDR in mind to start with at least)
So my recommendation is still to just be sure you've setup the system HDR Calibration correctly as suggested for you TV and that's it, but the HDR rendition even when doing so will still be mediocre compared to actually native HDR titles.
Enjoy,
-P